Analysis of the nature and sequence of cytokines and microbial products required for development of the fully activated macrophage wasthelong term goal of the principal investigator's original proposal. The recent availability of recombinant cytokines, cytokine-specificantibodies, highly purifiedpreparations of lipopolysaccharides, and synthetic lipid A analogs, and the new development of molecular techniques in the principal investigator'slaboratory have enabled her to makesignificant progresstoward characterization of cellular and molecular mechanisms controlling macrophage surfacemarkers and functions during development. Continued use of macrophages derived from the endotoxin hyporesponsive C3H/HeJ mouse strain hasenabled assessment of the contributions of LPS and cytokines to macrophage differentiation. Four specific aims areproposed, in studies with C3H/HeJ mice, normal mice, and knockoutmice: (1) To analyze the LPS signaling pathway in macrophages with specialemphasis on those aspects of the signaling pathways that are shared by LPS and taxol. (2) Todelineate the role of specific genes in macrophage differentiation using both primary macrophages and macrophage cell lines derived from knockoutmice. (3) To analyzethe role of interferon consensus sequence-binding protein (ICSBP) in macrophage differentiation. (4) To analyzefurtherthe molecularregulation of specific macrophage differentiation markers.